Generally, most wheelchairs of prior art technique, which are employed for transporting of invalid persons or of weaker or ill persons being unable to walk themselves, are made in conformity with the above described technique of prior art, i.e. they comprise a chassis, generally a frame shaped chassis, which through suitably suspended wheels, the suspension means thereby comprising suitable spring means and being of per se known kind, carries four ground-engaging wheels of suitable size, of which wheels two may be fitted to the chassis with one on each of two opposite sides of the chassis, the wheels being carried through a common in cross direction arranged wheel axle or through two separate wheel axles, which are arranged sharing a common geometric axis, and whereby the further two of the ground-engaging wheels are steerably suspended in that their steering axes are vertically oriented, and in that in general two of the ground-engaging wheels are connected to a wheel drive means and are made steerable as described above as from a steering control panel situated as suitable within easy reach of the person being transported by the wheel chair.
With such an arrangement of the ground-engaging wheels, in general they are arranged as in case of a common rear-wheel-driven automobile, though the suspension structures for the wheels do have a more simple structural shape, because they only are going to be operated at fairly low drive speeds. On the other hand, the steering wheels are suspended in such a manner so that geometrically the vertical steering axis is located in front of the wheel axles whereby in per se well known manner a self correcting straight forward driving can be maintained.
This usually employed kind of structure for a wheelchair suffers under more than one drawback. Such a wheelchair can not be described as being particularly steerable, and in case of more complicated steering such as for steering to achieve a close passing of larger objects, furniture, etc., in narrow environments require the use of reverse to bring the rear wheels to follow a correct track. A sideward directed driving of the wheel chair is not attainable in a fairly easy manner except to bring about more small to and from movements by the wheelchair, and thus only a kind of sideward zig-zag-driving may be the only sideward movement which in a somewhat awkward manner may be attainable.
Moreover, an oblique direction of approach while driving close to a table is only possible, whenever to and from driving are not wanted to be carried out, in the manner that the wheelchair, including the seat of it, are brought to attain an oblique oriented position as in relation to the edge of the table. It is thus easily understood that a person being seated in the chair also simultaneously in position has to be turned similarly oblique in relation to this same edge of the table. When a person being seated in the chair thus has to be brought to bed or has to be brought into the seat from a bed this is only possible when the front of the wheelchair is oriented so that it is turned straight forward towards to oblique towards the side or longitudinal edge of the bed, in such a situation substantial additional labor is required from an aiding person, as well when a person has to be passed from the wheelchair to the bed as when the person has to be moved in the opposite direction.